Zeng Ren Sen, Mallik Azim U
Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada.
J Chem Ecol. 2006 Jul;32(7):1473-89. doi: 10.1007/s10886-006-9063-6. Epub 2006 May 23.
Allelopathy has been implicated as a factor contributing toward failure of black spruce (Picea mariana) regeneration in Kalmia angustifolia-dominated sites in eastern Canada. Several phenolic acids of Kalmia origin inhibit primary root growth of black spruce. We tested the hypothesis that some well-adapted conifer ectomycorrhizae can degrade and detoxify water-soluble phenolic compounds produced by Kalmia and use the degraded products as a carbon source to stimulate growth. We found that hyphal growth of Paxillus involutus, a common ectomycorrhizal fungus of black spruce, was stimulated by water leachates of Kalmia leaf and litter. An equimolar mixture of three phenolic acids (ferulic, o-coumaric, and o-hydroxyphenylacetic acid), commonly found in Kalmia, had no negative effects on fungal growth at 1 mM concentration. The o-hydroxyphenylacetic (o-HPA) acid, which is known to be toxic to black spruce, was found to stimulate the growth of Laccaria laccata, L. bicolor, and P. involutus (isolates 211804 and 196554) by 38.4, 29.3, 25.0, and 18.9%, respectively, at 1 mM. Pure ferulic, o-coumaric, and o-HPA acids were degraded by 100, 98, and 79.5%, respectively, within 10 d in the presence of P. involutus 211804. However, L. laccata could not tolerate high concentrations of the Kalmia leachates. P. involutus and L. bicolor used o-HPA acid as a carbon source when cultured in noncarbon nutrient medium. The 0.5 and 0.2 mM o-HPA acid inhibited the root growth of black spruce. However, after solutions had been exposed to a culture of P. involutus, they had no significant effect on seedling growth of black spruce. We concluded that some ectomycorrhizal fungi, such as P. involutus and L. bicolor, are able to degrade Kalmia phenolics. Our findings point to a mechanism by which ectomycorrhizal species can control species interactions in higher plants by changing the rhizosphere chemistry.
化感作用被认为是导致加拿大东部以狭叶山月桂为主的地区黑云杉（Picea mariana）更新失败的一个因素。狭叶山月桂产生的几种酚酸会抑制黑云杉初生根的生长。我们检验了这样一个假设：一些适应性良好的针叶树外生菌根能够降解并解毒狭叶山月桂产生的水溶性酚类化合物，并利用降解产物作为碳源来刺激生长。我们发现，黑云杉常见的外生菌根真菌卷缘桩菇（Paxillus involutus）的菌丝生长受到狭叶山月桂叶片和凋落物的水浸提液的刺激。狭叶山月桂中常见的三种酚酸（阿魏酸、邻香豆酸和邻羟基苯乙酸）的等摩尔混合物在1 mM浓度下对真菌生长没有负面影响。已知对黑云杉有毒的邻羟基苯乙酸（o-HPA）在1 mM浓度下分别刺激了乳白红菇（Laccaria laccata）、双色蜡蘑（L. bicolor）和卷缘桩菇（分离株211804和196554）的生长，刺激率分别为38.4%、29.3%、25.0%和18.9%。在卷缘桩菇211804存在的情况下，纯阿魏酸、邻香豆酸和邻羟基苯乙酸在10天内分别降解了100%、98%和79.5%。然而，乳白红菇无法耐受高浓度的狭叶山月桂浸提液。在无碳营养培养基中培养时，卷缘桩菇和双色蜡蘑将邻羟基苯乙酸用作碳源。0.5 mM和0.2 mM的邻羟基苯乙酸抑制了黑云杉的根系生长。然而，当溶液与卷缘桩菇培养物接触后，它们对黑云杉幼苗生长没有显著影响。我们得出结论，一些外生菌根真菌，如卷缘桩菇和双色蜡蘑，能够降解狭叶山月桂酚类物质。我们的研究结果指出了一种外生菌根物种可以通过改变根际化学来控制高等植物物种间相互作用的机制。
